Method and apparatus for secondary base station change in mobile wireless communication system

ABSTRACT

A method and apparatus for secondary base station change in a mobile communication system are provided. Method for secondary node change includes receiving conditional reconfiguration information from the base station, transmitting to the base station a first response message with a transaction identifier, performing evaluation based on the configuration generated by a second base station and transmitting a second response message with an identifier indicating which conditional reconfiguration is executed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2021-0103268, filed on Aug. 5, 2021, the disclosureof which is incorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates to a mobile communication system withsecondary base station change. More specifically, the present disclosurerelates to a secondary node change method and an apparatus for use inthe mobile communication system with multiple subcarrier spacings.

To meet the increasing demand for wireless data traffic since thecommercialization of 4th generation (4G) communication systems, the 5thgeneration (5G) system is being developed. For the sake of high, 5Gsystem introduced millimeter wave (mmW) frequency bands (e. g. 60 GHzbands). In order to increase the propagation distance by mitigatingpropagation loss in the 5G communication system, various techniques areintroduced such as beamforming, massive multiple-input multiple output(MIMO), full dimensional MIMO (FD-MIMO), array antenna, analogbeamforming, and large-scale antenna. In addition, base station isdivided into a central unit and plurality of distribute units for betterscalability. To facilitate introduction of various services, 5Gcommunication system targets supporting higher data rate and smallerlatency.

SUMMARY

Aspects of the present disclosure are to address the problems ofconditional secondary node change. Accordingly, an aspect of the presentdisclosure is to provide a method and an apparatus for providing theconfiguration information for conditional secondary node change.

In accordance with an aspect of the present disclosure, a method of aterminal in mobile communication system is provided. In the method, UEreceives from the MN a 1st LTE DL message including a 1st NR DL messageand a 1st identity, transmits to the MN a 2nd LTE UL message includingthe 1st identity, performs conditional reconfiguration evaluation basedon measurement configuration configured by a SN or measurementconfiguration configured by the MN and transmits to the MN a 3rd LTE ULmessage including a 2nd identity. Conditional reconfiguration evaluationis performed based on measurement configuration configured by the SN ifa 2nd information indicating measurement configuration being associatedwith SCG is included in a 1st NR control information. The 1st NR DLmessage includes a plurality of the 1st NR control informations, andeach of the plurality of the 1st NR control informations includes a 2ndidentity, a 2nd information and a 2nd NR downlink control message, andthe 2nd identity is selected from a plurality of 2nd identities includedin the 1st NR downlink control message.

According to embodiments of the present disclosure, conditionalreconfiguration evaluation can be configured by SN.

According to embodiments of the present disclosure, MN can recognizewhich conditional reconfiguration is executed based on the 2ndidentifier reported by UE.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the architecture of an LTE system andan E-UTRAN to which the disclosure may be applied;

FIG. 2 is a diagram illustrating a wireless protocol architecture in anLTE system to which the disclosure may be applied;

FIG. 3 is a diagram illustrating the architecture of an 5G system and aNG-RAN to which the disclosure may be applied;

FIG. 4 is a diagram illustrating a wireless protocol architecture in an5G system to which the disclosure may be applied;

FIG. 5 is a diagram illustrating the architecture of an EN-DC to whichthe disclosure may be applied;

FIG. 6A is a diagram illustrating EN-DC operation performed by a UE anda base station according to the first embodiment of the presentdisclosure;

FIG. 6B is a diagram illustrating another EN-DC operation performed by aUE and a base station according to the first embodiment of the presentdisclosure;

FIG. 7 is a diagram illustrating a structure of LTE reconfigurationmessage for the 1st reconfiguration procedure;

FIG. 8 is a flow diagram illustrating an operation of a terminalaccording to the first embodiment of the present disclosure;

FIG. 9 is a flow diagram illustrating an operation of a master basestation according to the first embodiment of the present disclosure;

FIG. 10 is a block diagram illustrating the internal structure of a UEto which the disclosure is applied;

FIG. 11 is a block diagram illustrating the configuration of a basestation according to the disclosure;

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms used, in the following description, for indicating accessnodes, network entities, messages, interfaces between network entities,and diverse identity information is provided for convenience ofexplanation. Accordingly, the terms used in the following descriptionare not limited to specific meanings but may be replaced by other termsequivalent in technical meanings.

In the following descriptions, the terms and definitions given in the3GPP standards are used for convenience of explanation. However, thepresent disclosure is not limited by use of these terms and definitionsand other arbitrary terms and definitions may be employed instead.

In the following descriptions, UE and terminal are used as sameterminology.

Table 1 lists the acronyms used throughout the present disclosure.

TABLE 1 Acronym Full name 5GC 5G Core Network 5GS 5G System 5QI 5G QoSIdentifier ACK Acknowledgement AMF Access and Mobility ManagementFunction ARQ Automatic Repeat Request AS Access Stratum ASN.1 AbstractSyntax Notation One BSR Buffer Status Report BWP Bandwidth Part CACarrier Aggregation CAG Closed Access Group CAG-ID Closed Access GroupIdentifier CG Cell Group CHO Conditional Handover CIF Carrier IndicatorField CORESET Control Resource Set CPC Conditional PSCell Change CQIChannel Quality Indicator C-RNTI Cell RNTI CSI Channel State InformationDC Dual Connectivity DCI Downlink Control Information DRB (user) DataRadio Bearer DRX Discontinuous Reception ECGI E-UTRAN Cell GlobalIdentifier eNB E-UTRAN NodeB EN-DC E-UTRA-NR Dual Connectivity EPCEvolved Packet Core EPS Evolved Packet System E-RAB E-UTRAN Radio AccessBearer ETWS Earthquake and Tsunami Warning System E-UTRA EvolvedUniversal Terrestrial Radio Access E-UTRAN Evolved Universal TerrestrialRadio Access Network FDD Frequency Division Duplex FDM FrequencyDivision Multiplexing GBR Guaranteed Bit Rate HARQ Hybrid AutomaticRepeat Request HPLMN Home Public Land Mobile Network IDC In-DeviceCoexistence IE Information element IMSI International Mobile SubscriberIdentity KPAS Korean Public Alert System L1 Layer 1 L2 Layer 2 L3 Layer3 LCG Logical Channel Group MAC Medium Access Control MBR Maximum BitRate MCG Master Cell Group MCS Modulation and Coding Scheme MeNB MastereNB MIB Master Information Block MIMO Multiple Input Multiple Output MMEMobility Management Entity MN Master Node MR-DC Multi-Radio DualConnectivity NAS Non-Access Stratum NCGI NR Cell Global Identifier NE-DCNR-E-UTRA Dual Connectivity NGEN-DC NG-RAN E-UTRA-NR Dual ConnectivityNG-RAN NG Radio Access Network NR NR Radio Access NR-DC NR-NR DualConnectivity PBR Prioritised Bit Rate PCC Primary Component CarrierPCell Primary Cell PCI Physical Cell Identifier PDCCH Physical DownlinkControl Channel PDCP Packet Data Convergence Protocol PDSCH PhysicalDownlink Shared Channel PDU Protocol Data Unit PLMN Public Land MobileNetwork PRACH Physical Random Access Channel PRB Physical Resource BlockPSCell Primary SCG Cell PSS Primary Synchronisation Signal PUCCHPhysical Uplink Control Channel PUSCH Physical Uplink Shared Channel PWSPublic Warning System QFI QoS Flow ID QoE Quality of Experience QoSQuality of Service RACH Random Access Channel RAN Radio Access NetworkRA-RNTI Random Access RNTI RAT Radio Access Technology RB Radio BearerRLC Radio Link Control RNA RAN-based Notification Area RNAU RAN-basedNotification Area Update RNTI Radio Network Temporary Identifier RRCRadio Resource Control RRM Radio Resource Management RSRP ReferenceSignal Received Power RSRQ Reference Signal Received Quality RSSIReceived Signal Strength Indicator SCC Secondary Component Carrier SCellSecondary Cell SCG Secondary Cell Group SCS Subcarrier Spacing SDAPService Data Adaptation Protocol SDU Service Data Unit SeNB SecondaryeNB SFN System Frame Number S-GW Serving Gateway SI System InformationSIB System Information Block (S-/T-) SN (Source/Target) Secondary NodeSpCell Special Cell SRB Signalling Radio Bearer SRS Sounding ReferenceSignal SSB SS/PBCH block SSS Secondary Synchronisation Signal SULSupplementary Uplink TDD Time Division Duplex TDM Time DivisionMultiplexing TRP Transmit/Receive Point UCI Uplink Control InformationUE User Equipment UL-SCH Uplink Shared Channel UPF User Plane Function

Table 2 lists the terminologies and their definition used throughout thepresent disclosure.

TABLE 2 Terminology Definition Cell combination of downlink andoptionally uplink resources. The linking between the carrier frequencyof the downlink resources and the carrier frequency of the uplinkresources is indicated in the system information transmitted on thedownlink resources. Global cell An identity to uniquely identifying anNR cell. It is consisted of cell- identity Identity and plmn-Identity ofthe first PLMN-Identity in plmn- IdentityList in SIB1. gNB nodeproviding NR user plane and control plane protocol terminations towardsthe UE, and connected via the NG interface to the 5GC. Information Astructural element containing single or multiple fields is referred aselement information element. NR NR radio access PCell SpCell of a mastercell group. Primary SCG For dual connectivity operation, the SCG cell inwhich the UE Cell performs random access when performing theReconfiguration with Sync procedure. Serving Cell For a UE inRRC_CONNECTED not configured with CA/DC there is only one serving cellcomprising of the primary cell. For a UE in RRC_CONNECTED configuredwith CA/DC the term ‘serving cells’ is used to denote the set of cellscomprising of the Special Cell(s) and all secondary cells. SpCellprimary cell of a master or secondary cell group. Cell Group in dualconnectivity, a group of serving cells associated with either the MeNBor the SeNB. En-gNB node providing NR user plane and control planeprotocol terminations towards the UE, and acting as Secondary Node inEN-DC. Master Cell in MR-DC, a group of serving cells associated withthe Master Node, Group comprising of the SpCell (PCell) and optionallyone or more SCells. Master node in MR-DC, the radio access node thatprovides the control plane connection to the core network. It may be aMaster eNB (in EN-DC), a Master ng-eNB (in NGEN-DC) or a Master gNB (inNR-DC and NE-DC). NG-RAN node either a gNB or an ng-eNB. PSCell SpCellof a secondary cell group. Secondary For a UE configured with CA, a cellproviding additional radio Cell resources on top of Special Cell.Secondary in MR-DC, a group of serving cells associated with theSecondary Cell Group Node, comprising of the SpCell (PSCell) andoptionally one or more SCells. Secondary in MR-DC, the radio accessnode, with no control plane connection to node the core network,providing additional resources to the UE. It may be an en-gNB (inEN-DC), a Secondary ng-eNB (in NE-DC) or a Secondary gNB (in NR-DC andNGEN-DC). Conditional a PSCell change procedure that is executed onlywhen PSCell PSCell execution condition(s) are met. Change gNB Central alogical node hosting RRC, SDAP and PDCP protocols of the gNB or Unit(gNB-CU) RRC and PDCP protocols of the en-gNB that controls theoperation of one or more gNB-DUs. The gNB-CU terminates the F1 interfaceconnected with the gNB-DU. gNB a logical node hosting RLC, MAC and PHYlayers of the gNB or en- Distributed gNB, and its operation is partlycontrolled by gNB-CU. One gNB-DU Unit (gNB-DU) supports one or multiplecells. One cell is supported by only one gNB- DU. The gNB-DU terminatesthe F1 interface connected with the gNB-CU. E-RAB An E-RAB uniquelyidentifies the concatenation of an S1 Bearer and the corresponding DataRadio Bearer. When an E-RAB exists, there is a one-to-one mappingbetween this E-RAB and an EPS bearer of the Non Access Stratum (NAS) asdefined in TS 23.401 [3].

Table 3 lists abbreviations of various messages, information elementsand terminologies used throughout the present disclosure.

TABLE 3 Abbreviation Message/IE/Terminology LTE RECNFRRCConnectionReconfiguration LTE RECNF CMPRRCConnectionReconfigurationComplete CAPENQ UECapabilityEnquiry CAPINFUECapabilityInformation NR RECNF RRCReconfiguration NR RECNF CMPRRCReconfigurationComplete ULIT ULInformationTransferMRDC SGNB ADD REQSGNB ADDITION REQUEST SGNB ADD REQ SGNB ADDITION REQUEST ACK ACKNOWLEDGESGNB REL REQ SGNB RELEASE REQUEST SGNB REL REQ SGNB RELEASE REQUEST ACKACKNOWLEDGE SGNB RECNF CMP SGNB RECONFIGURATION COMPLETE Transaction IDrrc-TransactionIdentifier TCSPCELL Target Candidate SpCell CRIDCondReconfigurationId

Table 4 explains technical terminologies used throughout the presentdisclosure.

TABLE 4 Terminology Definition PSCell change It means the current PSCellchanges to a new PSCell. It includes intra-SN PSCell change and inter-SNPSCell change. PSCell addition is also considered as PSCell change.CG-ConfigInfo IE The IE is transferred from MN to SN or from CU to DU.It includes following information ue-CapabilityInfo includes variousinformation for UE capability MeasResultList2NR includes measurementresults on the candidate cells for serving cell DRX configuration of MCGCG-Config IE The IE is transferred from SN to MN or from CU to DU. Itincludes following information NR RRCReconfiguration which includes SCGconfiguration informatino. MN transfer the NR RRCReconfiguration messageto UE without modifying it Information related to SCG bearer. Itincludes the information indicating the security key for the bearer DRXconfiguration of SCG ARFCN indicating the center frequency of PSCellmeasConfig It is configuration related to measurement and set by MN andSN separately. It comprises at least one measurement object(measObject), at least one report configuration (ReportConfig) and atleast one measurement identity (measId). A measObject is identified by aMeasObjectId. A reportConfig is identified by a ReportConfigId. A measIdcomprises a measObjectId and a reportConfigId. MeasId instructs UE toperform a specific operation when measurement result on the associatedmeasObject fulfils condition set by ReportConfigId TCSPCELL It indicatestarget candidate SPCell. In the 1^(st) procedure, plurality of cells ofa single target node can be configured as target candidate SpCell.TCSPCELL can be a cell selected, by MN or S-SN, among the cells forwhich UE report measurement result. Throughout the 1^(st) procedure, oneof plurality of TCSPCELL becomes PSCell

FIG. 1 is a diagram illustrating the architecture of an LTE system andan E-UTRAN to which the disclosure may be applied.

The E-UTRAN consists of eNBs (102, 103, 104), providing the E-UTRA userplane (PDCP/RLC/MAC/PHY) and control plane (RRC) towards the UE. TheeNBs (102, 103, 104) are interconnected with each other by means of theX2 interface. The eNBs are also connected to the MME (MobilityManagement Entity) (105) and to the Serving Gateway (S-GW) (106) bymeans of the S1. The S1 interface supports a many-to-many relationbetween MMEs/Serving Gateways and eNBs. MME (105) and S-GW (106) may berealized either as a physical node or as separate physical nodes.

The eNB (102, 103, 104) hosts the functions listed below.

Functions for Radio Resource Management such as Radio Bearer Control,Radio Admission Control, Connection Mobility Control, Dynamic allocationof resources to UEs in uplink, downlink and sidelink(scheduling); and IPand Ethernet header compression, uplink data decompression andencryption of user data stream; and

Selection of an MME at UE attachment when no routing to an MME can bedetermined from the information provided by the UE; and

Routing of User Plane data towards Serving Gateway; and

Scheduling and transmission of paging messages (originated from theMME).

The MME (105) hosts the functions such as NAS signaling, NAS signalingsecurity, AS security control, S-GW selection, Authentication, Supportfor PWS message transmission and positioning management.

The S-GW (106) hosts the functions such as packet routing andforwarding, transport level packet marking in the uplink and thedownlink, mobility anchoring for inter-eNB handover etc.

FIG. 2 is a diagram illustrating a wireless protocol architecture in anLTE system to which the disclosure may be applied.

User plane protocol stack consists of PDCP (201 or 202), RLC (203 or204), MAC (205 or 206) and PHY (207 or 208). Control plane protocolstack consists of NAS (209 or 210), RRC (211 or 212), PDCP, RLC, MAC andPHY.

Each protocol sublayer performs functions related to the operationslisted in the table 5.

TABLE 5 Sublayer Functions NAS authentication, mobility management,security control etc RRC System Information, Paging, Establishment,maintenance and release of an RRC connection, Security functions,Establishment, configuration, maintenance and release of SignallingRadio Bearers (SRBs) and Data Radio Bearers (DRBs), Mobility, QoSmanagement, Detection of and recovery from radio link failure, NASmessage transfer etc. PDCP Transfer of data, Header compression anddecompression, Ciphering and deciphering, Integrity protection andintegrity verification, Duplication, Reordering and in-order delivery,Out-of-order delivery etc. RLC Transfer of upper layer PDUs, ErrorCorrection through ARQ, Re- segmentation of RLC data PDUs,Concatenation/Segmentation/Reassembly of SDU, RLC re-establishment etc.MAC Mapping between logical channels and transport channels,Multiplexing/demultiplexing of MAC SDUs belonging to one or differentlogical channels into/from transport blocks (TB) delivered to/from thephysical layer on transport channels, Scheduling information reporting,Priority handling between UEs, Priority handling between logicalchannels of one UE etc. PHY Channel coding, Physical-layer hybrid-ARQprocessing, Rate matching, Scrambling, Modulation, Layer mapping,Downlink Control Information, Uplink Control Information etc.

FIG. 3 is a diagram illustrating the architecture of an 5G system and aNG-RAN to which the disclosure may be applied.

5G system consists of NG-RAN (301) and 5GC (302). An NG-RAN node iseither:

-   -   a gNB, providing NR user plane and control plane protocol        terminations towards the UE; or    -   an ng-eNB, providing E-UTRA user plane and control plane        protocol terminations towards the UE.

The gNBs (305 or 306) and ng-eNBs (303 or 304) are interconnected witheach other by means of the Xn interface. The gNBs and ng-eNBs are alsoconnected by means of the NG interfaces to the 5GC, more specifically tothe AMF (Access and Mobility Management Function) and to the UPF (UserPlane Function). AMF (307) and UPF (308) may be realized as a physicalnode or as separate physical nodes.

A gNB (305 or 306) or an ng-eNBs (303 or 304) hosts the functions listedbelow.

Functions for Radio Resource Management such as Radio Bearer Control,Radio Admission Control, Connection Mobility Control, Dynamic allocationof resources to UEs in uplink, downlink and sidelink(scheduling); and

IP and Ethernet header compression, uplink data decompression andencryption of user data stream; and Selection of an AMF at UE attachmentwhen no routing to an MME can be determined from the informationprovided by the UE; and

Routing of User Plane data towards UPF; and

Scheduling and transmission of paging messages; and

Scheduling and transmission of broadcast information (originated fromthe AMF or O&M); and

Measurement and measurement reporting configuration for mobility andscheduling; and

Session Management; and

QoS Flow management and mapping to data radio bearers; and

Support of UEs in RRC_INACTIVE state; and

Radio access network sharing; and

Tight interworking between NR and E-UTRA; and

Support of Network Slicing.

The AMF (307) hosts the functions such as NAS signaling, NAS signalingsecurity, AS security control, SMF selection, Authentication, Mobilitymanagement and positioning management.

The UPF (308) hosts the functions such as packet routing and forwarding,transport level packet marking in the uplink, QoS handling and thedownlink, mobility anchoring for mobility etc.

FIG. 4 is a diagram illustrating a wireless protocol architecture in an5G system to which the disclosure may be applied.

User plane protocol stack consists of SDAP (401 or 402), PDCP (403 or404), RLC (405 or 406), MAC (407 or 408) and PHY (409 or 410). Controlplane protocol stack consists of NAS (411 or 412), RRC (413 or 414),PDCP, RLC, MAC and PHY.

Each protocol sublayer performs functions related to the operationslisted in the table 6.

TABLE 6 Sublayer Functions NAS authentication, mobility management,security control etc RRC System Information, Paging, Establishment,maintenance and release of an RRC connection, Security functions,Establishment, configuration, maintenance and release of SignallingRadio Bearers (SRBs) and Data Radio Bearers (DRBs), Mobility, QoSmanagement, Detection of and recovery from radio link failure, NASmessage transfer etc. SDAP Mapping between a QoS flow and a data radiobearer, Marking QoS flow ID (QFI) in both DL and UL packets. PDCPTransfer of data, Header compression and decompression, Ciphering anddeciphering, Integrity protection and integrity verification,Duplication, Reordering and in-order delivery, Out-of-order deliveryetc. RLC Transfer of upper layer PDUs, Error Correction through ARQ,Segmentation and re-segmentation of RLC SDUs, Reassembly of SDU, RLCre-establishment etc. MAC Mapping between logical channels and transportchannels, Multiplexing/demultiplexing of MAC SDUs belonging to one ordifferent logical channels into/from transport blocks (TB) deliveredto/from the physical layer on transport channels, Scheduling informationreporting, Priority handling between UEs, Priority handling betweenlogical channels of one UE etc. PHY Channel coding, Physical-layerhybrid-ARQ processing, Rate matching, Scrambling, Modulation, Layermapping, Downlink Control Information, Uplink Control Information etc.

FIG. 5 is a diagram illustrating the architecture of an EN-DC to whichthe disclosure may be applied.

E-UTRAN supports MR-DC via E-UTRA-NR Dual Connectivity (EN-DC), in whicha UE is connected to one eNB (501 or 502) that acts as a MN and oneen-gNB (503 or 504) that acts as a SN. The eNB (501 or 502) is connectedto the EPC (505) via the S1 interface and to the en-gNB (503 or 504) viathe X2 interface. The en-gNB (503 or 504) might also be connected to theEPC (505) via the S1-U interface and other en-gNBs via the X2-Uinterface.

LTE and NR are expected to coexist for considerable time to come. Asingle operator could deploy both LTE and NR within its network. Forsuch ease, providing to a UE both stable connection with LTE and highdata rate with NR is possible if UE is connected to both. EN-DC enablessimultaneous data transfer via LTE and NR.

In EN-DC, frequent SN change could happen due to narrow coverage of NR.SN change requires PSCell change, so they are technically synonymous.PSCell change procedure in general is consisted with that MN or S-SN getaware that PSCell change is needed, that T-SN determines theconfiguration of the new PSCell and that MN informs UE the configurationof the new PSCell. Depending on a given circumstances, eitherimmediately changing the PSCell upon receiving the PSCell configurationinformation or changing PSCell when certain condition is met could beappropriate. In the disclosure, the latter is 1^(st) reconfiguration(delayed reconfiguration or conditional reconfiguration) and the formeris 2^(nd) reconfiguration (or immediate reconfiguration or normalreconfiguration).

The disclosure provides operations of the terminal and the base stationfor the 1^(st) reconfiguration and for the 2^(nd) reconfiguration.

FIG. 6A is a diagram illustrating EN-DC operation performed by a UE anda base station according to the first embodiment of the presentdisclosure. FIG. 6B is a diagram illustrating another EN-DC operationperformed by a UE and a base station according to the first embodimentof the present disclosure.

In 610, MN (602) decides SN change based on measurement result reportedby UE (601).

MN (602) transmits, to T-SN (604), SGNB ADD REQ requesting resourceallocation for the UE's EN-DC operation. SGNB ADDREQ includes followinginformation.

1. 1^(st) information: Information indicating whether SGNB additionprocedure is for 1^(st) reconfiguration or for 2^(nd) reconfiguration.

2. 2^(nd) information: It is included If 1^(st) reconfiguration isrequested. 1^(st) reconfiguration execution condition and relatedinformation determined by MN. It includes execution condition andexecution condition cell group IE.

3. Measurement results on T-SN's cells

4. Data radio bearer configuration related information: Information onDRBs to be established. It can be used for T-SN's call admissioncontrol.

5. Maximum data rate related information: Expected maximum data rate ofthe call. It can be used for T-SN's call admission control.

The 1^(st) information can be realized by various embodiments.

1^(st) reconfiguration and 2^(nd) reconfiguration can be distinguishedby introducing new code point in SGNB Addition Trigger Indication IE. Inthe current specifications, SGNB Addition Trigger Indication IE isdefined to indicate one of SN change, inter-eNB HO and intra-eNB HO. Inthis disclosure, new code point called Conditional PSCell Change isadditionally defined for SGNB Addition Trigger Indication IE. If the IEindicates one of SN change, inter-eNB HO and intra-eNB HO, it is for the2^(nd) reconfiguration procedure. If the IE indicates Conditional PSCellChange, it is for the 1^(st) reconfiguration procedure.

Alternatively, Conditional PSCell Change (CPC) IE can be introduced toindicate the 1^(st) reconfiguration procedure. CPC IE can indicatewhether the corresponding procedure is to replace the currentconditional reconfiguration or to initiate new conditionalreconfiguration. Or a list of cells determined based on measurementresults from UE, for example list of TCSPCELLs, can be used as the1^(st) information.

In 615, T-SN (604) performs call admission control and decides whetherto accept the request or not. If decide to accept, T-SN (604) sends, toMN (602), SGNB ADD REQ ACK.

The message includes information on the resource allocated to the UE,for example IE related to maximum data rate, IE related to radio bearer,logical identity to identify UE on X2 interface and Cell groupconfiguration (CG-Config) IE. The message also includes a 3^(rd)information indicating whether the procedure is 1^(st) reconfigurationprocedure or 2^(nd) reconfiguration procedure. The 3^(rd) informationcan be a specific cell's global identity and maximum number ofConditional PSCell Change/Addition preparations for a UE toward a targetGNB.

MN (602) determines whether to perform 1^(st) reconfiguration procedureor 2^(nd) reconfiguration procedure. If MN transmitted 1^(st)information and 2^(nd) information and received 3^(rd) information, MNperforms 1^(st) reconfiguration procedure. If MN did not transmit 1^(st)information and 2^(nd) information and did not receive 3^(rd)information, MN performs 2^(nd) reconfiguration procedure. If MN decidesto perform 1^(st) reconfiguration procedure, MN proceed to 620.

In 620, MN (602) transmits to UE (601) 1^(st) LTE RECNF.

The structure of LTE RECNF to configure 1^(st) reconfiguration for EN-DCUE is explained in FIG. 7 .

If 1^(st) LTE RECNF includes ExecRepConfig, UE proceeds to 635 uponcompletion of 630. If 1^(st) LTE RECNF does not include ExecRepConfig,UE proceeds to 660 upon completion of 630.

ExecRepConfig is to instruct UE to report it when the 1^(st)reconfiguration is executed. It can be a 1 bit indicator or a list ofbearers whose status on data reception/transmission is to be reported.

In 625, UE transmits to MN 1^(st) LTE RECNF CMP comprising 1^(st)Transaction id.

Optionally, UE determines execution condition based on executioncondition IE and execution condition cell group IE. The executioncondition IE comprises one or two MeasId(s). The execution conditioncell group IE is information indicating either master cell group (or MN)or secondary cell group (or SN). Alternatively, the informationindicates only master cell group and absence of the information can beinterpreted as secondary cell group being indicated. MeasId in theexecution condition IE is the MeasId of the MeasConfig of the cell groupindicated by execution condition cell group IE. UE considers the MeasIdof the indicated cell group's MeasConfig as the execution condition. UErecognize which measurement object to measure, and which conditiontriggers the 1^(st) reconfiguration execution based on the variousparameters of MeasObject associated with the MeasId and based on thevarious parameters of ReportConfig associated with the MeasId.

The execution condition is determined by MN or S-SN. MN or S-SN expressthe determined execution condition using a MeasId defined in itsMeasConfig. UE needs to know which node between MN and SN sets theexecution condition to recognize what the MeasId really means. In thedisclosure, above information is indicated to the UE via executioncondition cell group IE.

In LTE, MeasId indicating a value between 1 and 32 and MeasId-v1250indicating a value between 33 and 64 are defined. In the disclosure,former is 5 bit measId and latter is 5 bit measId-ext. In NR, MeasIdindicating a value between 1 and 64 is defined. In the disclosure, it is6 bit measId.

MN can inform T-SN measId for execution condition via SGNB ADD REQ. MNcan transform a 5 bit measId or a 5 bit measId-ext to 6 bit measId andinclude it in SGNB ADD REQ. If MN selects a 1^(st) 5 bit measId forexecution condition, MN sets the MSB of 6 bit measId to 0 and setsremaining of 6 bit measId to the 1^(st) 5 bit measId. If MN selects a2^(nd) 5 bit measId for execution condition, MN sets the MSB of 6 bitmeasId to 1 and sets remaining of 6 bit measId to the 2^(nd) 5 bitmeasId.

UE receives 6 bit measId for the execution condition via RECNF. If theexecution condition is determined by S-SN, UE determines the executioncondition without transforming 6 bit measId. If the execution conditionis determined by MN, UE determines the execution condition bytransforming 6 bit measId either to 1^(st) 5 bit measId or to 2^(nd) 5bit measId.

In 630, UE performs conditional reconfiguration evaluation to determinewhether condition for conditional reconfiguration is fulfilled. UEdetermines whether measurement result for a cell corresponding to thecell identity indicated in 3^(rd) NR RECNF (i.e. TCSPCELL) fulfillsexecution condition. If so, UE executes conditional reconfiguration byapplying 2^(nd) NR RECNF of the cell fulfilling the execution condition.

In 635, UE generates ExecutionReport control message and transmits it toMN. ExecutionReport can include following information.

1. List of SCG bearers that require data forwarding. It can be a list ofE-RAB identities or a list of DRBs. Data is forwarded from S-SN to T-SNvia MN. Depending on the result of call admission control of T-SN, onlypart of SCG bearers currently configured can be accepted by T-SN.Bearers for data forwarding are those that pass call admission controland requires data forwarding. MN request S-SN data forwarding based onthe information

2. List of SCG bearers for release: List of bearers to be released basedon T-SN's call admission control.

3. For each bearer requiring data forwarding, the highest PDCP COUNTvalue of PDCP SDUs received so far and PDCP COUNT values for reorderedPDCP SDUs

4. CRID: CRID corresponding to 2^(nd) NR RECNF having triggeredexecution of 1^(st) reconfiguration.

In 640, MN (602) transmits SGNB REL REQ to S-SN (603) so that requiredsteps such as SN STATUS TRANSFER procedure can be taken. SGNB REL REQincludes GTP tunnel information for data forwarding. MN can include, inthe SGNB REL REQ, PDCP COUNT of the first PDCP PDU for data forwardingfor each bearer requiring data forwarding.

In 642, S-SN (603) receives SGNB REL REQ, starts a specific timer andtransmits SGNB REL REQ ACK to T-SN (604). S-SN (603) releases theresource allocated to the UE and discard related information upon expiryof the timer.

In 645, S-SN (603) transmits to MN (602) SN STATUS TRANSFER includinguplink/downlink PDCP SN and HFN. MN forward it to T-SN (604). SN STATUSTRANSFER includes HFN and PDCP SN.

T-SN (604) determines, based on SN STATUS TRANSFER, HFN and PDCP SN ofdownlink PDCP packet to be transmitted to UE and PDCP SN of uplink PDCPpackets for which retransmission is to be requested.

In 647, S-SN (603) forwards PDCP packets to MN. MN forwards them to T-SN(604). T-SN (604) transmits those downlink PDCP packets to UE. S-SN canperform data forwarding based on PDCP COUNT of the first PDCP PDU fordata forwarding.

In 650, UE performs random access procedure with T-SN. During randomaccess procedure, UE transmits preamble to a base station, the basestation transmits random access response to the UE, UE performs PUSCH(Physical Uplink Shared Channel) transmission toward the base stationand the base station transmits contention resolution message to UE.

In 655, UE transmits ULIT to MN. ULIT includes 1^(st) NR RECNF CMP.1^(st) NR RECNF CMP includes 3^(rd) Transaction id. If MN receives ULITfrom UE with ongoing 1^(st) reconfiguration procedure, MN recognizesthat the 1^(st) reconfiguration is executed and performs requiredactions. For example, MN forwards to T-SN 1^(st) NR RECNF CMP includedin ULIT and initiates SGNB release procedure with S-SN.

In 657, MN transmits SGNB RECNF CMP to T-SN. The message includes 1^(st)NR RECNF CMP. SN recognize the 1^(st) NR RECNF CMP is the response to2^(nd) NR RECNF from that 1^(st) NR RECNF CMP includes 3^(rd)Transaction id. Afterward UE, MN and T-SN performs data transfer viaEN-DC operation.

Steps from 640 to 647 and steps from 650 to 657 are independentprocedures and time domain order of two procedures can change. Forexample, 650 can start during steps between 640 and 647 resulting inparallel progress of two procedures.

If 1^(st) RECNF received in 620 does not include ExeRepConfig, UEproceed to 660 after 630.

In 660, UE performs random access procedure with T-SN. During randomaccess procedure, UE transmits preamble to a base station, the basestation transmits random access response to the UE, UE performs PUSCH(Physical Uplink Shared Channel) transmission toward the base stationand the base station transmits contention resolution message to UE.

In 662, UE transmits ULIT to MN. ULIT includes 1^(st) NR RECNF CMP.1^(st) NR RECNF CMP includes 3^(rd) Transaction id. If MN receives ULITfrom UE with ongoing 1^(st) reconfiguration procedure, MN recognizesthat the 1^(st) reconfiguration is executed and performs requiredactions. For example, MN forwards to T-SN 1^(st) NR RECNF CMP includedin ULIT and initiates SGNB release procedure with S-SN.

In 665, MN transmits SGNB RECNF CMP to T-SN. The message includes 1^(st)NR RECNF CMP. SN recognize the 1^(st) NR RECNF CMP is the response to2^(nd) NR RECNF from that 1^(st) NR RECNF CMP includes 3^(rd)Transaction id. Afterward UE, MN and T-SN performs data transfer viaEN-DC operation

In 670, MN (602) transmits SGNB REL REQ to S-SN (603) so that requiredmeasures such as SN STATUS TRANSFER procedure can be taken. SGNB REL REQincludes GTP tunnel information for data forwarding. MN can include, inthe SGNB REL REQ, PDCP COUNT of the first PDCP PDU for data forwardingfor each bearer requiring data forwarding.

In 672, S-SN (603) receives SGNB REL REQ, starts a specific timer andtransmits SGNB REL REQ ACK to T-SN (604). S-SN (603) releases theresource allocated to the UE and discard related information upon expiryof the timer.

In 675, S-SN (603) transmits to MN (602) SN STATUS TRANSFER includinguplink/downlink PDCP SN and HFN. MN forward it to T-SN (604). SN STATUSTRANSFER includes HFN and PDCP SN.

T-SN (604) determines, based on SN STATUS TRANSFER, HFN and PDCP SN ofdownlink PDCP packet to be transmitted to UE and PDCP SN of uplink PDCPpackets for which retransmission is to be requested.

In 677, S-SN (603) forwards PDCP packets to MN. MN forwards them to T-SN(604). T-SN (604) transmits those downlink PDCP packets to UE. S-SN canperform data forwarding based on PDCP COUNT of the first PDCP PDU fordata forwarding.

As illustrated above, by transmitting to MN before initiating randomaccess procedure, data forwarding is triggered more quickly to shortenservice interruption time.

FIG. 7 is a diagram illustrating a structure of LTE reconfigurationmessage for the 1^(st) reconfiguration procedure

LTE RECNF includes 1^(st) Transaction id generated by MN and 1^(st) NRRECNF (702) generated by T-SN. 1^(st) NR RECNF includes variousinformation depending on the purpose of the related procedure. For the1^(st) reconfiguration, 1^(st) NR RECNF includesconditionalReconfiguration (710) which includes at least oneCondReconfigToAddMod IE (703 or 720 or 721).

Each CondReconfigToAddMod IE includes conditional ReconfigurationIdentity (or 2^(nd) NR control information identity) (704), executioncondition (705), execution condition cell group (722) and 2^(nd) NRRECNF (706) carrying various configuration information. 2^(nd) NRcontrol information identity is mandatorily present. Executioncondition, 2^(nd) NR RECNF and execution condition cell group areoptionally present. If the 2^(nd) NR control information identityincluded in the 2^(nd) NR control information is new identity, executioncondition and 2^(nd) NR RECNF are mandatorily present and executioncondition cell group is optionally present.

The 2^(nd) NR RECNF includes radio bearer configuration (708), counterfor security key (709) and 3^(rd) NR RECNF (707). The 3^(rd) NR RECNFincludes secondaryCellGroup IE which includes configuration informationof TCSPCELL.

Therefore, a single 1^(st) NR RECNF for 1^(st) reconfiguration procedureincludes plurality of TCSPCELL configuration information. Each ofplurality of TCSPCELL configuration information is associated with asingle execution condition IE and a single execution condition cellgroup IE.

The 1^(st) NR RECNF includes 2^(nd) Transaction ID, the 2^(nd) NR RECNFincludes 3^(rd) Transaction ID and the 3^(rd) NR RECNF includes 4^(th)Transaction ID,

FIG. 8 is a flow diagram illustrating an operation of a terminalaccording to the first embodiment of the present disclosure.

In 801, UE reports, to 1^(st) base station (MN or MeNB), UE capabilityrelated to EN-DC and 1^(st) reconfiguration procedure andExecutionReport

-   -   1^(st) capability information: a list of band combinations        supporting EN-DN    -   2nd capability information: a list of band combinations        supporting 1^(st) reconfiguration and EN-DC or list of EN-DC        band combinations supporting 1^(st) reconfiguration    -   3^(rd) capability information: a list of band combinations        comprising two NR bands    -   4^(th) capability information: 1 bit indicator indicating        ExecutionReport transmission support in EN-DC or LTE    -   5^(th) capability information: 1 bit indicator indicating        ExecutionReport transmission support in NE-DC or NR

2^(nd) capability information indicates NR band of which bandcombination, included in the 1^(st) capability information, supports1^(st) reconfiguration procedure. 2^(nd) capability informationindicates intra-band 1^(st) reconfiguration support.

3^(rd) capability information is list of band combinations with two NRbands and each band combination indicates inter-band 1^(st)reconfiguration is supported between the NR bands. For example, if (N1,N2) is included in 3^(rd) capability information, inter-band 1^(st)reconfiguration between N1 and N2 is supported. NR bands included in theband combinations of 3^(rd) capability information are the NR bandssupporting EN-DC.

A base station to which UE reports its capability, a base station fromwhich UE receives LTE RECNF and a base station with which UE performsrandom access can be different base stations. The reason is because thecapability reported by UE is stored in the core network and capabilityreporting is performed in the initial registration and not performedafterward.

In 806, UE receives LTE RECNF. The LTE RECNF includes 1^(st) NR RECNF.The 1^(st) NR RECNF includes 1^(st) information if the 1^(st) NR RECNFis for 1^(st) reconfiguration. The 1^(st) information includes at leastone 2^(nd) information. In the 2^(nd) information, a 3^(rd) informationand a 4^(th) information are mandatorily present, and a 5^(th)information is optionally present. Information from the 1^(st)information to the 5^(th) information are those defined between UE andbase station. They are different from the 1^(st) information to the3^(rd) information defined between MN and T-SN.

A 2^(nd) information corresponds to a TCSPCELL. A 3^(rd) informationcomprising one or two MeasId defines the execution condition for theTCSPCELL. A 4^(th) information is the 2^(nd) NR RECNF which includesradio bearer configuration, security key information and 3^(rd) NR RECNFfor the configuration information of TCSPCELL. 5^(th) informationindicates for which between MCG and SCG (or between MeNB and SgNB orbetween MN and S-SN) the execution condition is related to.

Each 3^(rd) information and each 5^(th) information define the executioncondition for each associated TCSPCELL (or associated 2^(nd)information). Alternatively, it is also possible to define a common3^(rd) information and a common 5^(th) information applicable to allcandidate SpCell (or all 2^(nd) information) included in the 1^(st) NRRECNF. It is possible to define he common 3^(rd) information and thecommon 5^(th) information as sub-IE of 1^(st) information. Then UEignores individual 3^(rd) information included under 2^(nd) information.UE applies common 3^(rd) information, if present, to all TCSPCELLsincluded in 1^(st) information. Otherwise, UE applies the 3^(rd)information included for each TCSPCELL.

The LTE RECNF may include 6^(th) information which is related toexecution report configuration and may include lower information such asSCG bearer list.

A single LTE RECNF includes a single 1^(st) NR RECNF. A single 1^(st) NRRECNF includes a single 6^(th) information and plurality of 2^(nd) NRRECNFs. A single 2^(nd) NR RECNF includes a single 3^(rd) NR RECNF.Therefore, a single LTE RECNF includes a plurality of 3^(rd) NR RECNFs,a plurality of 3^(rd) information, a plurality of 4^(th) information anda plurality of 5^(th) information. The number of 3^(rd) NR RECNFs, thenumber of 3^(rd) information and the number of 4^(th) information aresame while the number of 5^(th) information may be different. A singleRECNF includes a single Transaction id. The LTE RECNF includes 1^(st)Transaction id. The 1^(st) NR RECNF includes 2^(nd) Transaction id. The2^(nd) NR RECNF includes 3^(rd) Transaction id. The 3^(rd) NR RECNFincludes 4^(th) Transaction id.

In 811, UE transmits LTE RECNF CMP to the 1^(st) base station. The LTERECFN CMP includes 1^(st) Transaction id.

In 816, UE initiates 1^(st) reconfiguration if 1^(st) reconfigurationinformation is included in 1^(st) NR RECNF in 1^(st) LTE RECNF receivedby UE

In 821, UE determines, based on 3^(rd) information and 5^(th)information, to which cell group (or which node) MeasId indicated in the3^(rd) information is related. If 5^(th) information is absent, UEdetermines that execution condition for the corresponding TCSPCELL isset by S-SN and that the MeasId is related to source SCG (or S-SN). UEinterprets MeasId according to MeasConfig of source SCG (or S-SN). If5^(th) information is present, UE determines that execution conditionfor the corresponding candidate SpCell is set by MN and that the MeasIdis related to MCG (or MN). UE interprets MeasId according to MeasConfigof MCG (or MN). Alternatively, if 5^(th) information is present, UEdetermines that execution condition for the corresponding TCSPCELL isset by a CG (or by a node) between MCG and SCG (or between MN and S-SN)and UE interprets MeasId according to the MeasConfig of determined CG(or determined node).

In LTE, MeasId indicating a value between 1 and 32 and MeasId-v1250indicating a value between 33 and 64 are defined. In the disclosure,former is 5 bit measId and latter is 5 bit measId-ext. In NR, MeasIdindicating a value between 1 and 64 is defined. In the disclosure, it is6 bit measId.

MN can inform T-SN measId for execution condition via SGNB ADD REQ. MNcan transform a 5 bit measId or a 5 bit measId-ext to 6 bit measId andinclude it in SGNB ADD REQ. If MN selects a 5 bit measId for executioncondition, MN sets the MSB of 6 bit measId to 0 and sets remaining of 6bit measId to the 5 bit measId. If MN selects a 5 bit measId-Ext forexecution condition, MN sets the MSB of 6 bit measId to 1 and setsremaining of 6 bit measId to the 5 bit measId-Ext.

UE receives 6 bit measId for execution condition in RECNF. If theexecution condition is determined by S-SN, UE determines the executioncondition with 6 bit measId as it is. If the execution condition isdetermined by MN, UE determines the execution condition with 5 bitmeasId or 5 bit measId-Ext transformed from 6 bit measId. If MSB of 6bit measId is 0, UE takes the remaining 5 bit as 1^(st) 5 bit measId andselects associated ReportConfig and MeasObject accordingly. If MSB of 6bit measId is 1, UE takes the remaining 5 bit as 5 bit measId-Ext andselects associated ReportConfig and MeasObject accordingly.

In 826, UE performs conditional reconfiguration evaluation. For each2^(nd) information included in 1^(st) information, UE considers theserving cell indicated in 3^(rd) NR RECNF of 2^(nd) information (i.e.target candidate cell) as applicable cell. UE consider the targetcandidate cell as a triggered cell if event associated with the triggercondition for the cell is fulfilled. UE proceeds to 828 if at least onetriggered cell occur.

In 828, if execution report is configured, UE transmits to MNExecutionReport and proceeds to 831. If execution report is notconfigured, UE directly proceeds to 831. That execution report isconfigured means RECNF received from MN includes ExeRepConfig. UEincludes, in ExecutionReport, identity of bearer requiring dataforwarding, identity of bearer to be released and CRID. Thoseinformation are determined by control information included in 3^(rd) NRRECNF and CRID corresponding to 2^(nd) NR RECNF.

In 831, UE executes conditional reconfiguration. UE apply the 2^(nd) NRRECNF for the triggered cell.

In 836, UE transmits to 2^(nd) base station ULIT. ULIT includes 1^(st)NR RECNF CMP. 1^(st) NR RECNF CMP includes 3^(rd) Transaction id. ULITalso includes CRID corresponding to triggered cell (or 2^(nd) NR RECFNcorresponding to triggered cell)

FIG. 9 is a flow diagram illustrating an operation of a master nodeaccording to the first embodiment of the present disclosure.

In 901, 1 ^(st) base station transmits to 3^(rd) base station (T-SN)1^(st) control message related to SGNB addition. The 1^(st) controlmessage can include 1^(st) information and 2^(nd) information.

In 906, 1 ^(st) base station receives from 3^(rd) base station 2^(nd)control message related to SGNB addition. The 2^(nd) control message caninclude a 3^(rd) information and PSCell configuration information (ortarget SpCell configuration information). The 1^(st) base stationproceeds to 816 if 1^(st) condition is fulfilled. If the 1^(st) basestation has transmitted to 3^(rd) base station 1^(st) controlinformation which include 1^(st) information and has received 2^(nd)control information, from the 3^(rd) base station in response to the1^(st) control message, 1^(st) condition is fulfilled.

In 916, 1 ^(st) base station transmits to UE 1^(st) LTE RECNF whichincludes at least 1^(st) Transaction id and 1^(st) NR RECNF. 1^(st)Transaction id is determined and inserted by 1^(st) base station. 1^(st)NR RECNF is generated by 3^(rd) base station and transmitted to 1^(st)base station. 1^(st) NR RECNF includes at least one 2^(nd) Transactionid and plurality of 2^(nd) NR control information. 1^(st) base stationcan include, in 1^(st) LTE RECNF, information related to executionreport configuration. 1^(st) base station includes 6^(th) information inLTE RECNF.

In 921, 1^(st) base station receives, from UE, 1^(st) LTE RECNF CMPwhich includes 1^(st) Transaction id.

In 923, 1^(st) base station checks if, from UE, ExecutionReport isreceived before ULIT is received. If ExecutionReport is received beforeULIT, 1^(st) base station proceed to 931. If ULIT is received beforeExecutionReport, 1^(st) base station proceeds to 951. Or if bothExecutionReport and ULIT are received, 1^(st) base station performs from931 to 941. If only ULIT is received, 1^(st) base station performs 951to 958.

In 931, 1^(st) base station and 2^(nd) base station performs SGNBrelease procedure. In the procedure, 1^(st) base station transmits to2^(nd) base station SGNB REL REQ, 2^(nd) base station transmits to1^(st) base station SGNB REL REQ ACK. 1^(st) base station can includes,in SGNB REL REQ, some information received from ExecutionReport forexample PDCP COUNT of each bearer.

In 936, 1^(st) base station and 2^(nd) base station exchanges SN STATUSTRANSFER and performs data forwarding.

In 941, 1^(st) base station receives from UE ULIT which includes 1^(st)Transaction id and 1^(st) NR RECNF CMP. 1^(st) NR RECNF CMP includes atleast 3^(rd) Transaction id. 1^(st) base station transmits to 3^(rd)base station SGNB RECNF CMP, which includes at least 1^(st) NR RECNFCMP. 941 and 936 are independent procedures and time domain order ofthem can change. For example, 641 can start before 936 or during 936.

In 961, 1^(st) base station, UE and 3^(rd) base station complete theprocedure and performs EN-DC operation.

In 951, 1^(st) base station receives from UE ULIT, which includes 1^(st)Transaction id and 1^(st) NR RECNF CMP. 1^(st) NR RECNF CMP includes atleast 3^(rd) Transaction id. 1^(st) base station transmits to 3^(rd)base station SGNB RECNF CMP which includes at least 1^(st) NR RECNF CMP.

In 956, 1^(st) base station and 2^(nd) base station performs SGNBrelease procedure. In the procedure, 1^(st) base station transmits to2^(nd) base station SGNB REL REQ, 2^(nd) base station transmits to1^(st) base station SGNB REL REQ ACK.

In 958, 1^(st) base station and 2^(nd) base station exchanges SN STATUSTRANSFER and performs data forwarding.

In 961, 1^(st) base station, UE and 3^(rd) base station complete theprocedure and performs EN-DC operation.

FIG. 10 is a block diagram illustrating the internal structure of a UEto which the disclosure is applied.

Referring to the diagram, the UE includes a controller (1001), a storageunit (1002), a transceiver (1003), a main processor (1004) and I/O unit(1005).

The controller (1001) controls the overall operations of the UE in termsof mobile communication. For example, the controller (1001)receives/transmits signals through the transceiver (1003). In addition,the controller (1001) records and reads data in the storage unit (1002).To this end, the controller (1001) includes at least one processor. Forexample, the controller (1001) may include a communication processor(CP) that performs control for communication and an applicationprocessor (AP) that controls the upper layer, such as an applicationprogram. The controller controls storage unit and transceiver such thatUE operations illustrated in FIG. 8 are performed.

The storage unit (1002) stores data for operation of the UE, such as abasic program, an application program, and configuration information.The storage unit (1002) provides stored data at a request of thecontroller (1001).

The transceiver (1003) consists of a RF processor, a baseband processorand plurality of antennas. The RF processor performs functions fortransmitting/receiving signals through a wireless channel, such assignal band conversion, amplification, and the like. Specifically, theRF processor up-converts a baseband signal provided from the basebandprocessor into an RF band signal, transmits the same through an antenna,and down-converts an RF band signal received through the antenna into abaseband signal. The RF processor may include a transmission filter, areception filter, an amplifier, a mixer, an oscillator, adigital-to-analog converter (DAC), an analog-to-digital converter (ADC),and the like. The RF processor may perform MIMO and may receive multiplelayers when performing the MIMO operation. The baseband processorperforms a function of conversion between a baseband signal and a bitstring according to the physical layer specification of the system. Forexample, during data transmission, the baseband processor encodes andmodulates a transmission bit string, thereby generating complex symbols.In addition, during data reception, the baseband processor demodulatesand decodes a baseband signal provided from the RF processor, therebyrestoring a reception bit string.

The main processor (1004) controls the overall operations other thanmobile operation. The main processor (1004) process user input receivedfrom I/O unit (1005), stores data in the storage unit (1002), controlsthe controller (1001) for required mobile communication operations andforward user data to I/O unit (1005).

I/O unit (1005) consists of equipment for inputting user data and foroutputting user data such as a microphone and a screen. I/O unit (1005)performs inputting and outputting user data based on the mainprocessor's instruction.

FIG. 11 is a block diagram illustrating the configuration of a basestation according to the disclosure.

As illustrated in the diagram, the base station includes a controller(1101), a storage unit (1102), a transceiver (1103) and a backhaulinterface unit (1104).

The controller (1101) controls the overall operations of the main basestation. For example, the controller (1101) receives/transmits signalsthrough the transceiver (1103), or through the backhaul interface unit(1104). In addition, the controller (1101) records and reads data in thestorage unit (1102). To this end, the controller (1101) may include atleast one processor. The controller controls transceiver, storage unitand backhaul interface such that base station operation illustrated inFIG. 9 are performed.

The storage unit (1102) stores data for operation of the main basestation, such as a basic program, an application program, andconfiguration information. Particularly, the storage unit (1102) maystore information regarding a bearer allocated to an accessed UE, ameasurement result reported from the accessed UE, and the like. Inaddition, the storage unit (1102) may store information serving as acriterion to deter mine whether to provide the UE with multi-connectionor to discontinue the same. In addition, the storage unit (1102)provides stored data at a request of the controller (1101).

The transceiver (1103) consists of a RF processor, a baseband processorand plurality of antennas. The RF processor performs functions fortransmitting/receiving signals through a wireless channel, such assignal band conversion, amplification, and the like. Specifically, theRF processor up-converts a baseband signal provided from the basebandprocessor into an RF band signal, transmits the same through an antenna,and down-converts an RF band signal received through the antenna into abaseband signal. The RF processor may include a transmission filter, areception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC,and the like. The RF processor may perform a down link MIMO operation bytransmitting at least one layer. The baseband processor performs afunction of conversion between a baseband signal and a bit stringaccording to the physical layer specification of the first radio accesstechnology. For example, during data transmission, the basebandprocessor encodes and modulates a transmission bit string, therebygenerating complex symbols. In addition, during data reception, thebaseband processor demodulates and decodes a baseband signal providedfrom the RF processor, thereby restoring a reception bit string.

The backhaul interface unit (1104) provides an interface forcommunicating with other nodes inside the network. The backhaulinterface unit (1104) converts a bit string transmitted from the basestation to another node, for example, another base station or a corenetwork, into a physical signal, and converts a physical signal receivedfrom the other node into a bit string.

What is claimed is:
 1. A method by a terminal, the method comprising:receiving from a Master Node (MN) a first Downlink (DL) message, thefirst DL message includes a first identifier and one or more ConditionalReconfiguration Information Element (IE), each of the one or moreConditional Reconfiguration IE includes an execution condition and asecond identifier and a second DL message; transmitting, to the MN, afirst Long Term Evolution (LTE) Uplink (UL) message, the first LTE ULmessage includes the first identifier; performing a conditionalreconfiguration evaluation based on a measurement configurationassociated with Secondary Cell Group (SCG) if a first informationindicating a measurement identifier refers to the measurementconfiguration associated with SCG is included in the ConditionalReconfiguration IE; and transmitting to the MN a second LTE UL message,the second LTE UL message includes a New Radio (NR) UL message and thesecond identifier, the second identifier is one of one or more secondidentifiers included in the first DL message, the second identifiercorresponds to the second DL message that triggered conditionalreconfiguration.
 2. The method of claim 1, wherein the first identifieris a transaction identifier, and the second identifier is a conditionalreconfiguration identifier.
 3. The method of claim 1, wherein theexecution condition is determined based on 6 bit measurement identifierif the measurement configuration configured by a Secondary Node (SN) isused and the execution condition is determined based on 5 bitmeasurement identifier if the measurement configuration configured by MNis used.
 4. A terminal in a wireless communication system, the terminalcomprising: a transceiver configured to transmit and receive a signal;and a controller configured to control the transceiver to: receive froma Master Node (MN) a first Downlink (DL) DL message, the first DLmessage includes a first identifier and one or more ConditionalReconfiguration Information Element (IE), each of the one or moreConditional Reconfiguration IE includes an execution condition and asecond identifier and a second DL message; transmit to the MN a firstLong Term Evolution (LTE) Uplink (UL) LTE UL (Uplink) message, the firstLTE UL message includes the first identifier; perform a conditionalreconfiguration evaluation based on a measurement configurationassociated with Secondary Cell Group (SCG) if a first informationindicating a measurement identifier identity refers to the measurementconfiguration associated with SCG is included in the ConditionalReconfiguration IE; and transmit to the MN a second LTE UL message, thesecond LTE UL message includes a New Radio (NR) UL message and thesecond identifier, the second identifier is one of one or more secondidentifiers included in the first DL message, the second identifiercorresponds to the second DL message that triggered conditionalreconfiguration.
 5. A method by a base station, the method comprising:transmitting to a terminal a first Downlink (DL) message, the first DLmessage includes a first identifier and one or more ConditionalReconfiguration Information Element (IE), each of the one or moreConditional Reconfiguration IE includes an execution condition and asecond identifier and a second DL message; receiving from the terminal afirst Long Term Evolution (LTE) Uplink (UL) message, the first LTE ULmessage includes the first identifier; and receiving from the terminal asecond LTE UL message, the second LTE UL message includes a New Radio(NR) UL message and the second identifier, the second identifier is oneof one or more second identifiers included in the first LTE DL message,the second identifier corresponds to the second DL message thattriggered conditional reconfiguration, wherein a first informationindicating a measurement identifier refers to a measurementconfiguration associated with Secondary Cell Group (SCG) is included inthe Conditional Reconfiguration IE if a conditional reconfigurationevaluation is to be performed based on the measurement configurationassociated with SCG.